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3 Computer System Software Hardware InputOutput A Computer system is a collection of hardware and software.
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Problem-solving with Problem-solving with ComputersComputers
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OutlineOutlineComputer System
5 Steps for producing a computer program
Structured program and programming 3 types of control structure
Algorithm Tools for describing an algorithm Examples of algorithm and programs
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Computer SystemComputer System
Software
HardwareInput Output
A Computer system is a collection of
hardware and software.
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Computer SystemComputer System
Hardware the electric, electronic, and mechanical
equipment that makes up a computer
Software the series of instructions that tells the
hardware how to perform tasks
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Computer SystemComputer System Hardware : requires a series of instructions to
carry out its processing function.
Software : a group of instructions (computer program) which command a computer to take action and to make decision.
Without software, hardware is useless; hardware needs the instructions provides by software to process data into information.
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Computer Program Computer Program (Software)(Software)
A program is a sequence of instructions suitable for processing by a computer
Programs are written for controlling the computer hardware
o Instructions in a program tell the hardware to perform a task
for solving problems.
Without software, the hardware doesn’t know what to do !!
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Computer SystemComputer System
Algorithm describe the method in a sequence of steps to
get a computer to perform a task.
An Algorithm must be translated into a program by coding in a programming
language.
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Computer Program Computer Program (Software)(Software)
The activities of expressing an algorithm of a problem and translating the algorithm as a program is called programming.
The most fundamental concepts of computer science is programming and algorithm.
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5 Major Steps5 Major Steps for Producing a for Producing a Computer ProgramComputer Program
Problem Definition Understanding the problem
Problem Design Proposing the solution
Problem Coding Implementing the solution
Problem Testing Testing the solution
Problem Documentation Writing the document
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Problem DefinitionProblem Definition Have a clear understanding the problem
What we want to do specify objectives specify the desired input and output
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Problem DesignProblem Design Proposing the solution
Top-down design with modularity approach using hierarchy chart
Input/output and data structure design Algorithm design with certain tools
o Pseudocodeo Flowchart
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Problem CodingProblem Coding Implementing the solution
Write (code) the program from algorithm by using selected programming language
Program = Algorithm + Data Structure
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Problem TestingProblem Testing Testing the solution
Structured walk-through Desk checking Sample test data
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Problem DocumentationProblem Documentation Writing the document
User documentation Program documentation
Program Maintenance
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Structure Program and Structure Program and ProgrammingProgramming
Technique for organizing and coding computer programs Hierarchy of modules is used
Single entry Single exit point Control is passed downward through the
structure without unconditional branches to higher levels of the structure
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Structure Program and Structure Program and ProgrammingProgramming
Module A self-contained activities that contributes a
specific subtask.
The overall task is done in a logical order of the hierarchy of the subtasks.
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Example of Top-down Design Example of Top-down Design (with Modularity approach using a hierarchy chart)
Payroll System
Input Payment Processing Output
Compute Pay Compute Payroll Deduction
Regular Pay
Overtime Pay Payroll
SavingTax
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Problem Solving with Problem Solving with ComputerComputer
Problem
Solution in a computer program
Solution in a algorithm form
Difficult in solving big problem
Problem solving phase
Implementation phase
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Structure Program and Structure Program and ProgrammingProgramming
3 types of control flow (structure) Sequence Selection or branching Iteration or looping
Explain on the blackboard
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SequenceSequence
Statement #1Statement #2Statement #3
read X
read Y
Z = X + Y
print (“The sum of X and Y is ”, Z)
ExampleExample
Statement #1
Statement #2
Statement #3
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SelectionSelection
if condition then Statement #1 else Statement #2
condition
Statement #2 Statement #1
False True
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SelectionSelection
read X
read Y
if if ( X > Y ) then then print (“ X is greater than Y”)
elseelse print (“ Y is greater than X”)
ExampleExample
if condition then Statement #1 else Statement #2
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Iteration (Repeat Loop)Iteration (Repeat Loop)
repeat Statementsuntil condition
condition
Statements
False
True
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Iteration (Repeat Loop)Iteration (Repeat Loop)
repeat Statementsuntil condition
read X
read Y
repeat repeat print X
X = X+1
untiluntil (X >Y)
ExampleExample
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Iteration (While Loop)Iteration (While Loop)
while conditiondo Statements
condition
Statements
False
True
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Iteration (While Loop)Iteration (While Loop)
read X
read Y
while while (X<=Y)
do do print X
X = X+1
ExampleExample
while conditiondo Statements
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Iteration (For Loop)Iteration (For Loop)
for i = 1 to n do Statements
i <= ni <= n
Statements
False
1 i
i = i + 1
True
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Iteration (For Loop)Iteration (For Loop)
for i = 1 to n do Statements
read X
read Y
for for i = 1 to X
do do print (“The value of i is ”, i)
ExampleExample